From Biology-Online Dictionary | Biology-Online Dictionary
Revision as of 05:33, 19 March 2017 by Honeev (talk | contribs) (updated)


noun, plural: nuclei

(cell biology) The large, membrane-bounded organelle that contains the genetic material, in the form of multiple linear DNA molecules organized into structures called chromosomes

(botany) The central kernel of a nut or seed, or the center of a starch granule

(neuroanatomy) A group of cell bodies of nerve cells in the brain or spinal cord


In cell biology, the nucleus is an organelle dubbed as the central government o the cell. It is because it contains the genetic material that codes for the vital functions of the cell. The nucleus is the organelle responsible in maintaining the integrity of DNA and in controlling cellular activities such as metabolism, growth, and reproduction by regulating gene expression. The nucleus has three main components: the nucleolus, the chromatin and the nuclear envelope. The nuclear envelope has nuclear pores to control the movement of molecules between the nucleoplasm and the cytoplasm. Other minor components include Cajal bodies, Gemini of coiled bodies, polymorphic interphase karyosomal association, promyelocytic leukaemia bodies, paraspeckles, and splicing speckles. The nucleus is the largest organelle in animal cells. In mammalian cells, the average diameter is 6 µm. There are cells though that lack nuclei, such as human red blood cells.

In botany, the nucleus refers to the central kernel of a nut or seed, or the center of a starch granule. In neuroanatomy, a nucleus pertains to a cluster of cell bodies of nerve cells in the brain or spinal cord.

In other scientific fields, the term nucleus may generally refer to the core or the central part around which other parts are grouped or gathered. For instance, in Physics, a nucleus refers to the positively-charged center of an atom that usually contains the protons and neutrons. In Chemistry, a nucleus is a fundamental arrangement of atoms that occur in compounds through substitution of atoms without a change in structure. In Astronomy, a nucleus is the center of the head of a comet or the central or brightest part of a nebula or galaxy. In Meteorology, a nucleus is a particle on which water vapor molecules accumulate in free air to form water drops or ice crystals.

Word origin: L: kernel, syncopated var. of nuculeus, equiv. to nucu(la) little nut (nuc-, s. of nux nut + -ula -ULE) + -leus n. suffix.

See also:

Related term(s):

Related form(s):

  • nuclear (adjective)